1. Field of the Invention
The present invention relates to fastener driving tools such as pneumatic nail guns, power screwdrivers and staplers, and in particular to fastener driving tools having drive mode change devices.
2. Description of the Related Art
Known pneumatic nail guns have a drive mechanism that is disposed within a body and is driven by a compressed air. The drive mechanism is connected to a driver and is actuated by the operation of a trigger, so that the driver can reciprocally move to drive nails one after another out of a driver guide that extends from the body.
In order to prevent the nails from being accidentally driven, a contact arm is mounted on the body so as to extend downward from the lower end of the driver guide. When the contact arm has pressed against a workpiece, the contact arm slides upward relative to the driver guide to permit the trigger to actuate the drive mechanism. Thus, the driving operation of the nails can be performed only when the contact arm has moved upward.
Japanese Laid-Open Patent Publication No. 10-264052 teaches a pneumatic nail gun that includes a drive mode change device, so that the nail gun can operate in a first drive mode and a second drive mode. In the first drive mode, the drive mechanism can be actuated according to either a first sequence, in which the trigger is operated after the contact arm has moved upward, or a second sequence, in which the contact arm is moved upward after the trigger has been operated. In the second drive mode, the drive mechanism can be actuated according to only the first sequence. Therefore, a nail-on-nail driving operation can be reliably prevented.
The nail gun of this publication also includes a trigger lock mechanism that can prevent the nails from being accidentally driven during transportation or like occasions. Thus, the trigger lock mechanism can prevent a trigger from moving from an OFF position to an ON position, so that a nail drive mechanism will not be actuated even if a contact arm has been accidentally moved by contacting the other parts or objects during the transportation. Thus, the trigger lock mechanism serves to provide a drive inhibit mode.
However, the drive mode change device and the trigger lock mechanism are operated by different operation members from each other. Therefore, the operation for changing the drive mode between the first or second drive mode and the drive inhibit mode is very troublesome.
It is, accordingly, one object of the present invention to teach improved fastener driving tools. Preferably, such fastener driving tools can simplify the operation for changing the drive mode.
In one aspect of the present teachings, fastener driving tools may have a mode change device, which device enables a first drive mode, a second drive mode and a drive inhibit mode for a fastener drive mechanism. Preferably, the mode change device includes an operation member that is operable by an operator. The operation member may have a plurality of operational positions that correspond to the changeable modes. Preferably, the operation member is a single member.
Therefore, the operator is not required to operate different mode change devices in response to a change in the mode. In addition, the fastener driving tool may have a simple construction.
In a representative embodiment, the drive inhibit mode can be realized, for example, by preventing the trigger from moving from an OFF position to an ON position. Thus, this mode may provide a trigger lock function.
In the first drive mode, the fastener drive mechanism may be actuated when the trigger and a control member, which may be a contact arm, have been moved for actuating the fastener drive mechanism in either a first sequence or a second sequence. According to the first sequence, the trigger is moved from an OFF position to an ON position after the control member has moved from the second position to the first position. According to the second sequence, the trigger is moved from the first position to the second position after the trigger has moved from the OFF position to the ON position.
In the second drive mode, the fastener drive mechanism can be actuated only when the trigger and the control member are moved according to the first sequence.
In a preferred example, the operation member of the mode change device may be a support shaft that pivotally supports the trigger. Preferably, the support shaft may be rotatably supported by a tool body and may have a shaft portion, on which the trigger is pivotally supported. The support shaft may rotate relative to the body about a first axis, and the shaft portion may have a second axis that is displaced from the first axis. Therefore, the position of the first axis may change as the support shaft rotates, so that the path of the pivotal movement of the trigger changes in response to the rotational position of the support shaft. As a result, the operational relationship between the trigger and the control member or other parts of the tool that cooperate with the trigger may change, so that the different drive modes can be attained. This arrangement is advantageous, because the operation member serves as a support for the trigger and also serves as a part of the mode change device. Thus, a lock pin or like members for exclusively providing a trigger lock function as in the known tools are not required. Therefore, the construction of the tool about the trigger may be simplified.
In order to change the mode, the mode change device may change the position of a contact arm or an idler that may be mounted on the trigger. Thus, the mode can be changed by changing the positional relationship among the trigger and the other parts that cooperate with the trigger for actuating the fastener drive mechanism.
Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.